Drill Cuttings Measurement Box and System for Controlling Pilot Hole Drilling

ABSTRACT

A control system for a raise boring machine drilling a pilot hole and related methods are disclosed. The control system includes a cuttings box for receiving and weighing cuttings ejected from the pilot hole during drilling. The cuttings box is configured to retain an amount of cuttings indicative of advancing the pilot hole substantially the length of a drill rod. A controller in communication with the cuttings box is configured to receive a signal reflective of a weight of cuttings in the cuttings box. The controller is further configured to compare the received signal to an expected weight criteria associated with the drill rod length, and to in response to the signal satisfying the expected cutting weight criteria, have cuttings ejected from the cuttings box.

CROSS-REFERENCE TO RELATED APPLICATION(S

This application claims priority to U.S. Provisional Application No. 63/242,131 filed on Sep. 9, 2021, the contents of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The following generally relates to pilot hole drilling and methods for pilot hole drilling which include a drill cuttings measurement box.

BACKGROUND

A raise drill or raise boring machine (RBM) 10 is a mechanical device designed to excavate large diameter openings in hard rock. A raise 12 is started by drilling a pilot hole 14 (see FIG. 1A) from an upper area 16 to a lower breakthrough area 18 (see FIG. 1B). At the breakthrough area 18, the pilot bit 20 is removed and a large diameter reamer 22 is attached (see FIG. 1C). The excavation, or opening is called a raise 12 because the large cutter, or reamer 22 is “raised” up from below, pulled back towards the RBM 10 (see FIG. 1D). Raises 12 have been completed to a length over 600 m and to a diameter up to 6 m or more.

The pilot bit 20 and/or reamer 22 is/are attached to the RBM 10 with heavy, high capacity drill rods 24 that have a threaded connection at either end - a male thread at the pin end and a female thread at the box end. The drill rods 24 are hollow to reduce weight and to allow for the flow of water or other fluids (i.e., drilling fluids) to remove cuttings 26 when drilling the pilot hole 14. The water or other fluids are pumped into the pilot hole 14 via a pump. When drilling the pilot hole 14, cuttings 26 are ejected from the pilot hole 14 by flushing water through the center of the drill rods 24 to push the cuttings 26 out of the pilot hole 14 via the annular area or passage between the pilot bit 20 and the drill rod 24 - usually a 25 mm difference.

While creating the pilot hole 24, the RBM 10 is raised and lowered with a number of hydraulic cylinders 28. The hydraulic cylinders 28 are used with a hydraulic and/or electronic control system 30 to adjust and control the pressure in the hydraulic cylinders 28 for pilot hole 14 drilling.

Drilling pilot holes 14 usually requires adding additional drill rod(s) 24 to the drill string when the drilling depth of the existing drill rods 24 on the drill string is exhausted. Prior to adding another drill rod 24 to the drill string, and in addition to the flushing process during drilling, water is flushed through drill rods 24 to clear any cuttings 26 out from the pilot hole 14 (hereinafter referred to as flushing time between drilling rods). The flushing time is determined by operators on an individual basis exercising their judgement, adding an additional amount of time conducting flushing based on the drilling depth achieved by the previous drill rod.

Operators of an RBM 10 may unnecessarily extend the amount of flushing time. For example, an operator may extend the flushing time to avoid scenarios where a pilot hole 14 is not properly flushed resulting in one of: i) suspended cuttings 26 falling to back the bottom of the pilot hole 14 and plugging or immobilizing the pilot bit 20, ii) cuttings 26 plugging or immobilizing the drill string, or iii) cuttings 26 plugging the flushing water ports in the pilot bit 20. For example, the pilot bit 20 can be immobilized as a result of the cuttings 26 binding around the bottom stabilizers and preventing the drill string from rotating or moving up or down. A plugged or immobilized pilot bit 20 or drill string can be difficult, if even possible, to correct, possibly requiring the removal of the drill string from the pilot hole 14 or damaging drill rods or other equipment. Operators are also alert to a scenario where the flushing does not remove an adequate amount of cuttings 26 from pilot hole 14, resulting in similar damage.

When drilling a long, deep pilot hole 14, the unnecessarily extensions of flushing time can aggregate and result in a meaningful reduction in production. Moreover, in addition to lost production, increased flushing time also increases the costs associated with a drilling operation. Moreover, operators may be more likely to unnecessarily increase flushing time when drilling long deep holes as any corrective action would require an increasingly large amount of delay.

It is an object of the following to address at least one of the above-noted disadvantages.

SUMMARY

The following provides a system for controlling pilot hole drilling performed by an RBM 10. A control system is employed to prevent over or under flushing of a pilot hole 14 during the course of drilling. The control system as disclosed herein can provide a variety of advantages for any RBM 10. First, the time lost from unnecessary flushing may be reduced. In some instances, the flushing time may unnecessarily waste non-negligible time to use a RBM 10 drilling a deep hole 14. Second, adverse events can be detected more accurately, as increased flushing time is implemented according to existing cuttings and the imprecision associated with a system relying upon an operator’s judgement is avoided. Third, more accurate adverse events detection can be implemented to detect instances where too much cuttings 26 are being ejected from the pilot hole 14. Finally, the efficiency of additives such as liquid polymer to the drilling fluid can be monitored. As a result, more effective additives may be selected to respond to current or future applications or environments.

Two configurations are described for controlling pilot hole drilling in an RBM 10.

In one configuration, the pilot hole drilling is controlled at least in part based on the signal received from a cuttings measurement box, where the cutting measurement box is sized to an expected volume of cuttings for cutting a drill rod volume’s worth of subterranean material. In this way, the challenges associated with the flushing time set out above can be partially alleviated: whether the pilot hole is flushed is based on the amount of weight within the cuttings measurement box. Furthermore, by having the cuttings measurement box sized to the expected volume of cuttings for cutting a drill rod length’s worth of subterranean material, the system reduces complexity and can allow for in part automated operation. For example, the operator may be alerted of the appropriate time to add drill rods 24 to the drill string in response to a full cuttings measurement box (e.g., where the box contains the expected volume of cuttings for cutting a drill rod length’s worth of subterranean material), and reliance on operator’s judgements or relying on over flushing may be avoided.

In one configuration, a cutting measurement box is sized to an expected volume of cuttings for cutting a drill rod volume’s worth of subterranean material, and a signal from the cuttings measurement box is continually monitored. Continually monitoring the signal while a rod is being drilled can, rather than waiting to the end of the rod and then after the fact deciding that too little or too much material is in the box, give an indication of whether the drilling is proceeding at the expected rate.

In one aspect, a control system for a raise boring machine drilling a pilot hole and related methods are disclosed. The control system includes a cuttings box for receiving and weighing cuttings ejected from the pilot hole during drilling. The cuttings box is configured to retain an amount of cuttings indicative of advancing the pilot hole substantially the length of a drill rod. A controller in communication with the cuttings box is configured to receive a signal reflective of a weight of cuttings in the cuttings box. The controller is further configured to compare the received signal to an expected weight criteria associated with the drill rod length, and to in response to the signal satisfying the expected cutting weight criteria, have cuttings ejected from the cuttings box.

In another aspect, a control system for a raise boring machine drilling a pilot hole and related methods are disclosed. The control system includes a cuttings box for receiving and weighing cuttings ejected from the pilot hole during drilling. The cuttings box is configured to retain an amount of cuttings indicative of advancing the pilot hole substantially the length of a drill rod. A controller in communication with the cuttings box is configured to receive a signal reflective of a weight of cuttings in the cuttings box. The controller is further configured to compare the received signal to an expected weight criteria associated with the drill rod length, and to in response to the signal not satisfying the expected cutting weight criteria, generating an alert.

In a further aspect, a method of drilling a pilot hole is disclosed. The method includes initiating drilling with a drill rod, pumping drilling fluid into the pilot hole to eject cuttings from the pilot hole, and pumping the ejected cuttings into a cuttings box. The method includes generating a signal reflective of a weight of the cuttings in the cuttings box. In response to determining that the signal satisfies expected cutting weight criteria based on an amount of cuttings indicative of advancing the pilot hole substantially the length of the drill rod, the method includes ejecting cuttings from the cuttings box. A further drill rod is attached and drilling is reinitiated.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

Embodiments will now be described with reference to the appended drawings wherein:

FIGS. 1A - 1D illustrate a raise drilling operation using a raise boring machine 10.

FIG. 2 is a schematic diagram of an example system for controlling pilot hole drilling.

FIG. 3A is a perspective view of an example cuttings measurement box.

FIG. 3B is a top view of an example cuttings measurement box.

FIG. 3C is a bottom view of an example cuttings measurement box.

FIG. 4 is a perspective view of an example system for drilling pilot holes.

FIG. 5 illustrates a graph of example rate of penetration values.

FIG. 6A is a cross-sectional view of a portion of another example system for filling a pilot hole in an opened configuration.

FIG. 6B is a cross-sectional view of a portion of another example system for filling a pilot hole in an unopened configuration.

FIG. 7A is a block diagram illustrating an example method for drilling a pilot hole.

FIG. 7B is a block diagram illustrating another example method for drilling a pilot hole.

DETAILED DESCRIPTION

Referring now to the figures, FIG. 2 is a schematic diagram of an example system for controlling pilot hole drilling. The example configuration shown in FIG. 2 includes an RBM 10, a control system 30, a pump 32, a cuttings measurement box 34, and a drilling fluid source 36. It is understood that, in place of the RBM 10, the system may be used generally with drilling assemblies which drill holes into subterranean formations, and include for example mud as a drilling fluid, or any application where knowing the amount of material removed for a given length of drilled material while drilling at depth can reduce the risk of freezing a drill string. The system is understood to include any ancillary equipment used to assemble, disassemble and run the RBM 10, the control system 30, pump 32, cuttings measurement box 34, and drilling fluid source 36 and their related components.

Drilling fluid source 36 stores one or more drilling fluids 38 to be used to flush cuttings 26 from the pilot hole 14. The drilling fluid 38 within drilling fluid source 36 can be, for example, water, or optionally water treated with an additive 42 (e.g., a liquid polymer to increase the viscosity of the drilling fluid 36) from additive source 40, or various other compounds commonly referred to as “mud” and used in drilling operations. The additive 42 may be a powder, a liquid, a solid puck, etc. Additive source 40 may include different types of additive 42, and may output the different type of additive 42 based on different types of rock or other subterranean features encountered during the course of the drilling operation. In example embodiments, the additive source 40 is mixed in with the drilling fluid source 36. Additives from the additive source 40 may be added to the drilling fluid source 36 via, for example, pump 32, manually, or otherwise.

The system includes one or more pumps to (1) pump drilling fluid 38 into the pilot hole 14, and (2) to pump drilling fluid 38 and cuttings 26 accumulated in the pilot hole 14 out of the pilot hole 14. For example, in the embodiment shown in FIG. 2 , pump 32A is in fluid communication with the drilling fluid 38 entering the pilot hole 14 from the drilling fluid source 36. The pump 32A can be installed into a channel (e.g., the shown feeder pipeline 48) which carries drilling fluid 38 into the drill string or the pump 32 can be connected or installed into the drilling fluid source 36 directly (e.g., as is shown in FIG. 6A). Pump 32A may be a sump pump, a submersible pump, or any other pump capable of driving fluid 38 from the drilling fluid source 36 into the pilot hole 14. Furthermore, as set out above, in addition to driving drilling fluid 38 into and down the drill string, the system includes pump 32B which drives drilling fluid 38 and any accumulated cuttings 26 (hereinafter referred to as ejected fluid 46), out of pilot hole 14 and through the drill string. Pump 32B may be configured to drive the ejected fluid 46 through a channel (e.g., the shown exhaust pipeline 48) directly into the cuttings measurement box 34, or onto another conduit or surface (e.g., as shown in FIG. 6A). Pump 32B may be a sump pump, trash pump, a submersible pump, or any other pump capable of driving ejected fluid 46 from the pilot hole 14 into the cuttings measurement box 34. More than one pump may be used to fulfil the purpose of pumps 32A or 32B to generate the pressure gradient which pushes and/or pulls fluid 38 into the pilot hole 14, and pushes and/or pulls ejected fluid 46 into a channel to ejecting cuttings 26. Hereinafter, the term pump 32 shall be used to refer to the one or more pumps which can include pump 32A and 32B.

The pump 32 may operate according to one or more programmed duty cycles (e.g., on-and-off cycles), be operator controlled, be controlled by control system 30, or be controlled by a combination thereof. The pump 32 can be in communication with a control system display screen (not shown) accessible to the operator, and provide data such as, for example, an operating status (e.g., on/off), a remaining battery level (if battery-operated), an output pressure, a filter status, and so on.

Referring now to FIGS. 3A to 3C, cuttings measurement box 34 (hereinafter CMB 34) of the system receives the ejected fluid 46 through inlet 50 and retains therein at least cuttings 26 of the ejected fluid 46. The cuttings 26 can be retained with concrete walls 52, or other structures could be used to create a container. CMB 34 can include one or more perforations 54 within walls 52 which permit drilling fluid 38 within ejected fluid 46 to exit (e.g., flow through) the CMB 34 while retaining the cuttings 26. In the embodiment shown in FIG. 3A, example perforations 54 are visible only on a single wall 52 of CMB 34, however, it can be appreciated that perforations 54 can be included on any plurality of the walls 52. CMB 34 can also include a resealable outlet 56 (shown as a bottom door), which can be pivotable around one or more rotational members (shown as hinges 58 in this example). The resealable outlet 56 can move between an open configuration wherein cuttings 26 are ejected from CMB 34, and a closed configuration wherein cuttings 26 are accumulated and contained within the CMB 34. For example, the CMB 34 can include an actuator 60 to open or close the resealable outlet 56, where the actuator is powered by a power source 64 to rotate resealable cover 56 around rotational members 58.

The CMB 34 is configured to at least retain an amount of cuttings 26 associated with a drill rod 24 length H (FIG. 1D). For example, where a drill rod 24 of height H of h mm, having a diameter D of d inches, and the density of the subterranean formation being excavated is determined to be or expected to be ρ, the amount of cuttings 26 indicative of advancing the pilot hole 14 substantially the length of a drill rod 24 can be determined based on (1) modelling the drill rod as a cylinder, and estimating the volume of the drill rod 24 as 2 π r h, and (2) determining the expected weight of by multiplying the determined volume with the density ρ. The amount of cuttings 26 associated with a drill rod 24 length H can thereafter be based on the expected volume of the drill rod 24. In an illustrative example, a single drill rod on a string with a diameter of 355.6 mm (14 in) and a length of 1.52 m (60 in) will have a volume of 0.15135 m3 (9236.28 in3). The CMB 34 can also incorporate one or more allowances. For example, a swell factor (e.g., 20%) may be used to represent the possibibility that the volume of cuttings will not pack or occupy volume efficiently, and will occupy a greater space as compared to the packed arrangement in the subterranean environment. Similarly, the CMB 34 can be sized with a general allowance (e.g., 10%), increasing its usability between different drill rods, or generally allowing for other expansive factors. In example embodiments, the CMB 34 can be configured to retain at least part of the drilling fluid 38 of the ejected fluid 46, and the dimensions of the CMB 34 are based on an expected amount of drilling fluid 38 to be used for drilling a drill rod 24 length. Alternatively, the CMB 34 can be configured to retain an amount of cuttings 26 associated with multiple or a fractional amount of a drill rod 24 length. In example embodiments, the fractional CMB 34 would include an outlet system including at least two doors, so that the cuttings 26 within the CMB 34 could simultaneously eject and accumulate cuttings 26 still being ejected from the pilot hole 14. To account for cuttings 26 not intended to be ejected from the CMB 34 via the at least two door outlet system (e.g., there may be leakage of the cuttings 26 which have not contributed to the signal generated by the CMB 34) while drilling is ongoing, corresponding adjustments must be made to the expected weight criteria (as described herein) to account for a lower expected total weight. For example, the CMB 34 can be configured to retain the cuttings 26 expected to be ejected from pilot hole 14 drilling along half a length of drill rod 24. CMB 34 may be modular, or resizable, such that walls 52 may be moved or reinstalled to configure the CMB 34 to have a larger or smaller size, depending on the desired application.

CMB 34 also includes one or more sensors 62 (shown as sensors 62 a, 62 b, 62 c, and hereinafter referred to in the singular for ease of reference) which generate a signal reflective of the mass or volume of cuttings 26 retained within the CMB 34. Similar to the actuator 60, the sensor 62 can be connected to and powered by the power source 64. The sensor 56 may be mounted to CMB 34 such that the signal is reflective of both the mass or volume of cuttings 26 retained within the CMB 34, and the weight of the CMB 34 itself. For example, as shown in FIG. 3C, sensor 56 is located proximate to an end of a weight distributing support (e.g., elongated supports 66), which support the CMB 34 (e.g., via fasteners, adhesives, etc.) at a location other than the walls 52 of CMB 34. For example, the CMB 34 can rest on a platform specifically designed to support the CMB 34 at a fixed height relative to the drilling fluid source 36, as shown in FIG. 6A. The sensor 56 may include a microcontroller and generate digital signals of the sensed weight, or sensor 56 may provide an analog signal of the sensed weight (e.g., a voltage or current).

FIG. 4 illustrates an example of an assembly for a RBM 10 and control system 30, and is understood to include a RBM 10 and any ancillary equipment used to assemble, disassemble and run the RBM 10, including the control system 30 and its components. In this example, the RBM system includes a drill rig assembly 68 that includes the thrust cylinders 28 which are operable to drive the pilot bit 20 by adding or removing drill rods 24 during pilot drilling. Also shown are a hydraulic pack assembly 72 that includes the hydraulic control system components and a control console assembly 74, including a display 76 for a rig operator. An electric cabinet assembly 78 contains the electrical components for operating the control system 30 and RBM 10. The control system 30 can include a Programmable Automation Controller (PAC) or Programmable Logic Controller (PLC), or a controller comprising a processor for implementing the methods (e.g., FIG. 7A) as set out herein. The controller can be installed in an electric pack of RBM 10 and can include a remote adapter at a power pack of RMB 10, which power pack or remote adapter may have or allow for easier more connections to other devices and valves of RBM 10 as compared to console 76. Alternatively, controller of control system 30 can be within the console 76.

RBM 10 can further include a sensor 80, which measures the vertical distance the drill bit 24 has travelled during the drilling operation (e.g., how far into the subterranean formation the drill bit 24 has travelled). Sensor 80 can be a wireline encoder, an absolute encoder or an incremental encoder. In example embodiments where the sensor 80 is an absolute rotary encoder, the distance traveled by drill bit 24 is determined based on the number of rotations of thrust cylinders 28. Continuing the example, the absolute rotary encoder can have a resolution of 1,024 pulses per revolution (PPR) through a gear reducer (not shown) to extend the maximum range to match the maximum thrust cylinder stroke length. In example embodiments, RBM 10 can include a wireline encoder monitoring and measuring movement within a derrick or movable section of the RBM 10. Continuing the example, a draw wire (not shown) of the wireline encoder can be attached to a gearcase of RBM 10 that moves up and down. Preferably, the sensor 80 is fixed on the lower part of drill rig assembly 68 (as compared to a movable section) to avoid introducing additional cables pulsing up and down. Sensor 80 can be an incremental encoder, with additional modifications to instruct the control system 30 as to the top and bottom of a stroke of thrust cylinders 28 every time a thrust occurs. The sensor 80 can be configured be responsive and provide accurate data within a maximum of 10 to 15 seconds of the RBM 10 being activated for drilling operation and before the drill bit 24 has found the target drilling location and loading begins. In example embodiments, the sensor 80 is a system of distance measurers which includes one or more than one encoders, either of a single, or of multiples different types of encoders.

Rate of Penetration (ROP)

The control system 30 can be configured to receive a signal from the sensor 80, and to determine a ROP based on that signal. One solution to determining an accurate ROP can be to:

-   (1) receive the signal from the sensor 80 and calculate a position     of the movable section of RBM 10 in millimeters or inches, -   (2) Implement a first order low pass filter on the signal received     from the sensor 80. In example embodiments, the first order low pass     filter may be adjusted based on the drilling environment. The     control system 30 can be configured to implement or run this filter     as a special periodic task running every 50 milliseconds. -   (3) determine the ROP based on the filtered signal and a timer.

In an illustrative example, the control system 30 determines the ROP based in part on a first in first out (FIFO) array scheme, with a control system memory storing 300 elements or 300 samples of the sensor 80 signal. The first index of the array can be updated every 50 milliseconds, and all the other array elements are shifted so that the last index element is deleted. The first element less the last element can be used to determine the distance traveled during a period (e.g., 50 msec * 300 samples = 15 sec) and the duration of said travel.

The control system 30 can be configured to convert a determined ROP into a value which is commonly understood by an expected operator of control console assembly 74. For example, the determined ROP can be converted to inches per hour (in/h) by multiplying the value by 3600 then dividing by 12 to convert to feet per hour (ft/h).

Referring now to FIG. 5 , a graph illustrating an example ROP measurement is shown. Portion 90 of graph shows unfiltered data, which, relative to the middle portion 92 and the right portion 94 is much more erratic. The graph between portions 92 and 94 of the graph shows a ROP calculation which includes low pass filtering and provides a more consistent and usable results. For example, the sudden high/low jumps in FIG. 1 indicate that the RPM 10 being operated for a drill rod 24 change, and the regions which show other than said changes are clearer between portions 92 and 94 as compared to the unfiltered portion 90.

Net Bit Force (NBF)

During drilling, the control system 30 can also be configured to determine a NBF, which represents the net load on a pilot bit 20.

Virtually every RBM 10 has the same type of pressure control - manual or electronic volume and pressure control of the oil flow to a cap end of the hydraulic cylinders 28 when drilling. Oil flow to the cap end extends the thrust cylinders 28 and sets the maximum thrust loading of the pilot bit 20. That thrust loading also determines the amount of torque needed from the gearbox to rotate the drill string at that thrust level. For example, a hard formation pilot bit 20 will be loaded to a maximum thrust of 10,000 lbs per inch of diameter, or 160,000 lbs for a 16-inch bit.

In example embodiments, for example as described in U.S. Provisional Pat. Application Ser. No. 63/201,314, filed on Apr. 23, 2021, entitled “Stall Control System for Raise Drills and Raise Boring Machines”. which is incorporated by reference, in its entirety, into this disclosure, the thrust is controlled via a system wherein a further hydraulic control valve allows for a sudden release or venting of a fixed amount of pressurized oil from the rod end of the thrust cylinders 28.

Whether the system incorporates the hydraulic control valve (alternatively referred to as a “counterbalance valve”) of U.S. Provisional Pat. Application Ser. No. 63/201,314, or otherwise, a machine operator (or an automated routine) can activate a Bit Force Zero function to measure the cap and/or rod pressures while moving downward with drilling speed rate. In at least one embodiment, the bit force is determined with the following equations:

Bit Force = Downward Force - Upward Force

Where the downward force is measured with:

$\begin{array}{l} {\text{Downward Force = (Derrick Weight + (Drill String Weight} \times} \\ {\text{Bailing Medium Multiplier)} \times \text{Dip Angle Multiplier) +}} \\ {\text{(Rod End Pressure} \times \text{Rod End Area)}} \end{array}$

The bailing medium multiplier, for example, can be 1 for air and 0.87 for water.

The upward force is measured with:

Upward Force = Cap End Pressure × Cap End Area

The NBF indication at the control system 30 can be set to zero, so that any change in pressures following that with either a cap end drop or rod end rise will accurately calculate the bit force. The calculation incorporates the cross-sectional areas of the thrust cylinder 28 cap and rod ends so that a true net force can be determined. The RMB 10 can include some means of displaying either a gross bit force or NBF.

FIGS. 6A, 6B show, respectively, an unsealed and a sealed configuration of example CBM 634, having hinges 658 and a resealable outlet 656. As shown in FIGS. 6A, 6B, the CBM 634 is attached to wall of walls 682 which at least partially extend into the ground 684, wherein walls 682 define a box (e.g., a drilling fluid source 36) for retaining exhausted drilling fluid 638 leaving the pilot hole (not shown) and the CBM 634. The walls 682 can be, for example, built from concrete and sized to ensure a desired amount of drilling fluid 638 can be retained. Also shown in FIGS. 6A, 6B is a pad 686, which may be used to anchor or support at least in part the RBM 10, and a platform 688 which supports cuttings 626 as they are transported into CBM 634. The platform 688 can include a track 690 which is depicted in an exaggerated incline for illustrative purposes, to guide or support the cuttings 626 or drilling fluid 638 into the CBM 634. The elevation of track 690 may be selected to reduce the amount of pressure required to be generated by a pump 632 to pump fluid all the way back into walls 682. The track 690 may be perforated, such that only cuttings 636 are transported into the CBM 634. In example embodiments, track 690 is a pipe which carries both cuttings 626 and drilling fluid 638 directly into CBM 634.

Referring now to FIG. 7A, a block diagram illustrating a method of drilling a pilot hole is disclosed, with reference to the elements described in FIG. 2 .

At step 702, the drilling of pilot hole 14 is initiated. For example, the drilling may be initiated by an operator of RBM 10 via control system 30 after a new drill rod 24 has been loaded onto the drill string, or at the start of drilling the pilot hole 14.

In example embodiments, as a precursor to initiating drilling, the CMB 34 may be emptied or otherwise prepared for operation. The preparation can include controlling actuator 60 to open the CMB 34 to empty any contents therein. In example embodiments, the pump 32 includes a direct connection to the CMB 34, and preparation includes controlling pump 32 to drive drilling fluid 38 into the CMB 34 to wash away any debris. The preparation can also include a manual inspection and removal of any undesired substances. Once all removal steps have been completed, the control system 30 can run a logging or taring process, whereby subsequent signals received from the CMB 34 are measured relative to this logged signal of weight in the CMB 34.

At step 704, control system 30 transmits instructions or otherwise controls pump 32 to drive drilling fluid 38 into the pilot hole 14, flushing cuttings 26 from the pilot hole 14. As a precursor to, or simultaneous with pumping the drilling fluid 38 into the pilot hole 14, the control system 30 may pump additive 42 from additive source 40 into the drilling fluid source 36, such that drilling fluid 36 with additive 42 is pumped into the pilot hole 14.

At step 706, the CMB 34 generates and transmits a signal reflective of the weight of cuttings 26 inside the CMB 34. The CMB 34 may periodically generate the signal during timed intervals (e.g., every 10 milliseconds), based on feedback from other components of the RMB system10 (e.g., based on a pump running time, a NBF or a ROP), and so forth. The signal may be sent for display on a display screen of a control assembly (e.g., control console assembly 74), or be utilized or monitored by the control system 30.

At step 708, the control system 30 determines whether the signal indicates that the cuttings 26 have been flushed from the pilot hole 14. As described above, the control system 30 may display a “Yes” on an operator display where the weight of cuttings 26 in the CMB 34 satisfies an expected weight criteria associated with the expected drill rod 24 length. For example, the weight criteria may be a cumulative weight, or the weight criteria may also include a rate at which cuttings 26 enter the CMB 34.

In example embodiments, the expected weight criteria associated with the expected drill rod 24 length can include criteria reflective of a tolerance requirement. For example, the expected weight criteria associated with the expected drill rod 24 length can include a tolerance of plus or minus 20 lbs of cuttings 26, which criteria can be used in conjunction with an expected weight. Similarly, the expected weight criteria associated with the expected drill rod 24 length can include a tolerance criterion associated with an expected flow rate, such that sandy or looser cuttings 26 are expected to flow into the CMB 34 more steadily, whereas harder or more compact cuttings 26 may be expected to flow into CMB 34 more erratically. In example embodiments, the expected weight criteria can also include an expected weight of the drilling fluid 38 where drilling fluid 38 is at least in part retained in the CMB 34. In an illustrative example, where the signal from the CMB 34 does not satisfy the expected weight criteria owing to the signal being indicative of too much weight within the CMB 34, the signal may indicate the RMB 10 having encountered a seam of gravel or other material that was also being flushed from the pilot hole 14. In another illustrative example, where the signal from the CMB 34 does not satisfy the expected weight criteria owing to the signal being indicative of too little weight within the CMB 34, the signal may indicate that additional flushing of pilot hole 14 is required.

In the event that the signal from CMB 34 does not satisfy the expected weight criteria, the RBM 10 can be configured such that drilling cannot be recommenced without either additional flushing of pilot hole 14 until the signal is compliance, or with a manual operator override.

At step 710, the actuator 60 is controlled to open the CMB 34 to empty any contents therein. Step 710 may include adding a new drill rod 24 to the drill string prior to initiating drilling. As a result of the CMB 34 emptying contents every drill rod length, the CMB 34 can advantageously be relatively small, allowing for greater portability and reducing the amount of space required to be dedicated to the CMB 34 onsite.

Referring now to FIG. 7B, a block diagram illustrating an automated method of drilling a pilot hole is disclosed, with reference to the elements described in FIGS. 2, 6A and 6B.

At step 712, similar to step 702, drilling may be initiated. The drilling may only be initiated where a machine position received from the ROP sensor (e.g., the sensor 80) indicates that the NBF is zero. The drilling initiation procedure may also encompass actions similar to step 704 and step 710, where the CMB 634 is sealed and unsealed prior to commencing drilling with a new drill rod 24, and a new baseline signal to be used as a reference against subsequently flushed cuttings is established in order to aid automated drilling.

In example embodiments, prior to beginning drilling, the hydraulic cylinders 28 will be actuated until a threshold NBF is detected which indicates that the drill is at least in part engaged with the ground (i.e., a find-the-face threshold).

At step 716, the CMB 634 generates a signal representative of the weight of cuttings 626 within.

At step 714, a timer is commenced, the timer being intended to measure and display how long it will take for cuttings 626 to accumulate, above a set limit (e.g., an expected weight of an amount of cuttings indicative of advancing the pilot hole substantially the length of a drill rod), in the CMB 634. For example, the timer may be a timer function programmed into control system 30, or a separate timer operated on a microcontroller, or otherwise. The timer can track an aggregate time of operation, or track an estimated time until completion as discussed further herein, or track time for a preset duration (e.g., 5 minutes).

The timer, or control system 30, via logic programmed thereinto, and depending on the expected drilling rate and material being drilled into, can track an expected time until completion of an amount of cuttings 626 indicative of advancing the pilot hole 14 substantially the length of the drill rod 24. In example embodiments, the expected time until completion of a drill rod length of material is based on previous completion times for drilling a drill rod length. For example, prior to adding a fifth drill rod 24 to a drill string, the control system 30 may adjust an expected time until completion of a drill rod length of cuttings 626 based on an average of the drilling time of the four drill rods 24 preceding the fifth drill rod 24. The expected time until completion of a drill rod length can include an aggregate expected time for the full drilling operation which is dependent upon the desired depth of the pilot hole 14.

At step 718, the control system 30 receives the signal from the CMB 634 and according to one aspect determines whether to prevent further drilling, or according to another aspect determines whether to halt in progress drilling.

When drilling is in progress, the control system 30 can access preprogrammed or received/input data including the diameter of the pilot hole 14 being drilled, the specific gravity of the subterranean material being drilled, and the ROP to calculate and display an expected “Rate of Rock Drilled”. In an illustrative example, if the determined ROP is positive, the RBM 10 is traveling up when an operator joystick is in the up position and if the ROP is negative, the RBM 10 is traveling down when the operator joystick is in the down position. For determining the rate of rock drilled, in an embodiment where the theoretical maximum ROP for the RMB 10 is 5 ft/h or 60 in/h, and if the instantaneous ROP is greater than this maximum of 60 in/h or 0.017 in/sec, or negative when the joystick is in the up position, then the control system 30 may rely upon a previous ROP value is used. Similarly, if the ROP is less than -60 in/h or -0.017 in/sec or positive when the joystick is in the down position, the control system 30 may access and utilize the previous ROP value to determine the rate of rock drilled.

The rate of rock drilled and the signal from the CMB 634 is continuously monitored, and similar to step 706, where the expected weight criteria is not satisfied, the drilling process may be stopped. For example, the pilot hole 14 not being flushed properly may indicative of an expected weight criteria associated with the rate of weight accumulation and weight in the CMB 634 being unsatisfied.

In example embodiments, the control system 30 may track an effectiveness of a drilling fluid 38 based on the signal. For example, the signal may be monitored for changes in both accumulated weight and rate of weight accumulation within the CMB 634 where different additives 42 are used. For example, the additive 42 may be a liquid polymer, and drilling with and without the additive 42 may result in non-negligible differences in weight accumulation rate and overall weight accumulated in the CMB 634. The control system 30 may be configured to either actively test different additives 42, or track and display the most effective additive 42 used to date based on the received signals. In this way, the most effective additive 42 for the environment experienced by the RMB 10 in the operating environment may be calibrated. Where additives 42 are used or changed during operation, corresponding edits can be made to the expected weight criteria. For example, the expected weight criteria can include multipliers, or different values, for criteria based on the additive 42 used.

The expected weight criteria may also include one or more indicators of device malfunction. The one or more indicators of device malfunction can include indicators responsive to CMB 634, such as sensor 62 malfunctions, or otherwise. The indicators can be used to monitor unwanted correlations between RPM 10 operation and the signal received from CMB 634. In an illustrative example, the signal received from CMB 634 is expected to be increasing once the NBF trigger value had been reached and the RBM 10 is drilling into the subterranean formation. A signal that does not steadily increase can be indicative of malfunction. A signal which is materially different than a signal received during previous drilling periods with previous added drill rods can be indicative of malfunction. A signal which indicates an accumulated weight which is different than the previous accumulated weight can also be indicative of sensor 62 malfunctions. During establishment of a baseline for the signal, if the readings for the signal (e.g., measured from a 4-20 mA process input) for the elevated zero are too large, the signal may not satisfy expected weight criteria and indicate failure of the resealable outlet 56. Similarly, if the signal indicates a weight lower than a baseline weight during drilling, the signal may not satisfy expected weight criteria and indicate that the resealable outlet 56 has failed.

Where the signal does not satisfy expected weight criteria, the drilling may be stopped in a controlled fashion by control system 30, or an alarm may be generated, or the drilling may not be recommenced without subsequent operator input, and so forth. The alarm can be sent to an operator for monitoring, with different alarms having different severity indicators; for example a first alarm indicating a threshold being approached (yellow) and a second indicator where the threshold has been breached (red).

At step 720, similar to step 710, where the signal does satisfy the weight criteria the cuttings 626 are ejected from the CMB 634. For example, an actuator may open resealable outlet 656 via rotation around hinges 658. Once the cuttings 626 have been ejected, the process may be reset, with the system drilling and flushing additional cuttings 626 out of the pilot hole 14.

For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

It will be appreciated that the examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.

It will also be appreciated that any module or component exemplified herein that executes instructions may include or otherwise have access to computer readable media such as storage media, computer storage media, or data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by an application, module, or both. Any such computer storage media may be part of the controller or control system, any component of or related thereto, etc., or accessible or connectable thereto. Any application or module herein described may be implemented using computer readable/executable instructions that may be stored or otherwise held by such computer readable media.

The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified.

Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims. 

1. A control system for drilling a pilot hole using a raise boring machine, the control system comprising: a cuttings box for receiving and weighing cuttings ejected from the pilot hole during drilling, the cuttings box configured to retain an amount of cuttings indicative of advancing the pilot hole substantially the length of a drill rod ; a controller in communication with the cuttings box, the controller configured to receive a signal indicative of a weight of cuttings in the cuttings box, the controller further configured to: compare the received signal to an expected weight criteria associated with the drill rod length; and in response to the signal satisfying the expected cutting weight criteria, have cuttings ejected from the cuttings box.
 2. The system of claim 1, wherein the controller is further configured to: in response to determining the signal is below the expected cutting weight criteria, instruct a pump to increase a duration for pumping drilling fluid into the pilot hole to flush cuttings from the pilot hole.
 3. The system of claim 1, wherein the controller is further configured to: determine whether the signal satisfies a rate of rock drilled criterion of the expected cutting weight criteria; and in response to determining the signal is greater than the rate of rock drilled criterion, instruct the pump to cease pumping drilling fluid into the pilot hole.
 4. The system of claim 1, wherein the controller is further configured to: determine a first rate of change in the signal during a first period of operation conducted with a first additive; determine a second rate of change in the signal during a second period of operation conducted with a second additive; and in response to determining that the second rate of change is greater than a first rate of change, conduct further drilling with at least the second additive.
 5. The system of claim 1, wherein the controller is further configured to generate an alert in response to the received signal representing a decreasing weight of cuttings indicative of cuttings box failure.
 6. The system of claim 1, wherein one or more sidewalls of the cuttings box permit fluid passage through one or more perforations.
 7. The system of claim 1, wherein the cuttings box includes a resealable outlet connected to the controller, and wherein the instructions to eject cuttings from the pilot hole control an actuator to open the resealable outlet to eject accumulated cuttings.
 8. The system of claim 1, wherein the cuttings box is configured to generate signals according to a duration associated with the expected drill rod length.
 9. The system of claim 8, wherein the duration associated with the expected drill rod length is based on previous durations associated with the expected drill rod length.
 10. The system of claim 9, wherein the controller is further configured to: reset the expected cutting weight criteria associated with the amount of cuttings reflective of a drill rod length in response to the transmitting the instructions to eject cuttings from the pilot hole.
 11. A method of drilling a pilot hole, the method comprising: initiating drilling with a drill rod; pumping drilling fluid into the pilot hole to eject cuttings from the pilot hole; pumping the ejected cuttings into a cuttings box; generating a signal indicative of a weight of the cuttings in the cuttings box; in response to determining that the signal satisfies expected cutting weight criteria, ejecting cuttings from the cuttings box, wherein the expected cutting weight criteria being based on an amount of cuttings indicative of advancing the pilot hole substantially the length of the drill rod; and attaching a further drill rod and reinitiating drilling.
 12. The method of claim 11, comprising: in response to determining the signal is below the expected cutting weight criteria, pumping additional drilling fluid into the pilot hole to flush cuttings from the pilot hole prior to attaching the further drill rod and reinitiating drilling.
 13. The method of claim 11, comprising: determining whether the signal satisfies a rate of rock drilled criterion of the expected cutting weight criteria; in response to determining the signal is greater than the rate of rock drilled criterion, ceasing pumping of the drilling fluid into the pilot hole.
 14. The method of claim 11, comprising: determining a first rate of change in the signal during a first period of drilling conducted with a first additive; determining a second rate of change in the signal during a second period of drilling conducted with a second additive; in response to determining that the second rate of change is greater than a first rate of change, conducting further drilling with at least the second additive.
 15. The method of claim 11, comprising: generating an alert in response to the received signal representing a decreasing weight of cuttings indicative of cuttings box failure.
 16. The method of claim 11, wherein the signal is generated based on a duration associated with the amount of cuttings indicative of advancing the pilot hole substantially the length of the drill rod.
 17. The method of claim 11, wherein the duration associated with the amount of cuttings indicative of advancing the pilot hole substantially the length of the drill rod is based on previous durations for previous drill rods.
 18. A non-transitory computer readable medium for drilling a pilot hole, the computer readable medium comprising instructions for: initiating drilling with a drill rod; pumping drilling fluid into the pilot hole to eject cuttings from the pilot hole; pumping the ejected cuttings into a cuttings box; generating a signal indicative of a weight of the cuttings in the cuttings box; in response to determining that the signal satisfies expected cutting weight criteria, ejecting cuttings from the cuttings box, wherein the expected cutting weight criteria being based on an amount of cuttings indicative of advancing the pilot hole substantially the length of the drill rod; and attaching a further drill rod and reinitiating drilling. 